Recently, research and development efforts of technologies for a next-generation communication system have been intensively made in this technical field. In the next-generation communication system, it is assumed that a single-carrier method is to be employed in uplink transmission due to its reduced Peak-to-Average Power Ratio (PAPR) and wider coverage area.
Further, the radio resources are allocated in a format of the shared channel shared among plural users in accordance with the channel status of each user. The process of determining the allocation of the radio resources for transmitting a data channel or the like may be called “scheduling”. When the “scheduling” is performed, the base station properly allocates the frequencies and time (slots). Therefore, no contention occurs between different users. Because of this feature, the channel transmitted based on the scheduling may be called a scheduled channel or a contention-free channel. On the other hand, there is provided a channel for, for example, requesting to allocate resources. Such a channel may be called a contention-based channel or a random access channel (RACH). The random access channel (RACH) is transmitted at any timing and may be in conflict with the channel of other user apparatus. Heretofore, known random access channels (RACH) at the time of the present invention are described in Non Patent Document 1.
Non Patent Document 1: 3GPP, R1-061184, NTT DoCoMo et al., “Random Access Channel Structure for E-UTRA Uplink”, TSG RAN WG1 Meeting #45, Shanghai, China, 8-12 May, 2006